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61.
Guifang Zeng Yining Liu Chunyan Gu Kai Zhang Yongling An Chuanliang Wei Jinkui Feng Jiangfeng Ni 《物理化学学报》2020,36(5):1905006-0
Lithium-ion batteries (LIBs) are widely used in cellphones, laptops, and electric cars owing to their high energy density and long operational lifetime. However, their further deployment in large-scale energy storage systems is restricted by the uneven distribution of lithium resources (~0.0017% (mass fraction, w) in the Earth's crust). Therefore, alternative energy storage systems composed of abundant elements are of urgent need. Recently, sodium-ion batteries (SIBs) have attracted significant attention and are considered to be a potential alternative for next-generation batteries owing to abundant sodium resources (~2.64% (w) of the Earth's crust), suitable potential (−2.71 V), and low cost. SIBs are similar to LIBs in terms of their physical and electrochemical properties. Previous studies have mainly focused on SIB storage materials, including hard carbon, alloys, and hexacyanoferrate, while the safety of SIBs remains largely unexplored. Similar to LIBs, the current electrolytes used in SIBs are mainly composed of flammable organic carbonate solvents (or ether solvents), sodium salts, and functional additives, which pose possible safety issues. Moreover, the chemical activity of sodium is much higher than that of lithium, leading to a higher risk of fire, thermal runaway, and explosion. To overcome this problem, herein we propose a fluorinated non-flammable electrolyte composed of 0.9 mol∙L−1 NaPF6 (sodium hexafluorophosphate) in an intermixture of di-(2, 2, 2 trifluoroethyl) carbonate (TFEC) and fluoroethylene carbonate (FEC) in a 7 : 3 ratio by volume. Its physical and electrochemical properties were studied by ionic conductivity, direct ignition, cyclic voltammetry, and charge/discharge measurements, demonstrating excellent flame-retarding ability and outstanding compatibility with sodium electrodes. The electrochemical tests showed that the Prussian blue cathode retained a capacity of 84 mAh∙g−1 over 50 cycles in the prepared electrolyte, in contrast to the rapid capacity degradation in a flammable conventional carbonate electrolyte (74 mAh∙g−1 with 57% capacity retention after 50 cycles). To test the practical application of the proposed electrolyte, a hard carbon anode was used and exhibited exceptional performance in this system. The enhancement mechanism was further verified by Fourier transform infrared (FTIR), X-ray diffraction (XRD), and scanning emission microscopy (SEM) investigations. Polycarbonate on the surface of the cathode played an important role for the studied electrolyte system. The polycarbonate may originate from FEC decomposition, which can enhance the ionic conductivity of the solid electrolyte interface (SEI) layer and reduce impedance. Hence, we believe that this proposed electrolyte may provide new opportunities for the design of robust and safe SIBs for next-generation applications. 相似文献
62.
1 问题的提出
《数学通报》2006年7月1624号问题:若a1,a2,…,an∈R+,且a1+a2 +…+an=s,求证:1/a13(a2+a3+…+an)+1/a23(a1+a3+…+an)+…+1/an3(a1+a2+…+an-1)≥n5/s4(n-1).(1)
在2008年,罗邦华老师[1]利用一个不等式引理给出(1)证明,并将其结果进行了推广:若a1,a2,…,an∈R+,且a1+a2+…+an=s,|P|≥2,则n∑i=1 1/api(s-ai)≥np+2/sp+1(n-1).(2)
在2010年,翁利帅老师[2]分别利用构造不等式和函数凹凸性给出(1)的两种证明,并将(2)的条件| P |≥2再次推广到P∈(-∞,-1]U[0,+∞),(2)仍成立,但其推广证明较为复杂且在文中结语写:在推广过程中留下一点遗憾,未能对P∈(-1,0)的情况作出进一步的探究,望能与各位同行共同完善之. 相似文献
63.
Divergence-free wavelets are successfully applied to numerical solutions of Navier-Stokes equation and to analysis of incompressible
flows. They closely depend on a pair of one-dimensional wavelets with some differential relations. In this paper, we point
out some restrictions of those wavelets and study scaling functions with the differential relation; Wavelets and their duals
are discussed; In addition to the differential relation, we are particularly interested in a class of examples with the interpolatory
property; It turns out there is a connection between our examples and Micchelli’s work. 相似文献
64.
A weakly nonlinear model is proposed for the Kelvin-Helmholtz instability in two-dimensional incompressible fluids by expanding the perturbation velocity potential to third order. The third-order harmonic generation effects of single-mode perturbation are analyzed, as well as the nonlinear correction to the exponential growth of the fundamental modulation. The weakly nonlinear results are supported by numerical simulations. Density and resonance effects exist in the development of mode coupling. 相似文献
65.
孟凡申 《数学的实践与认识》2010,40(20)
得到了自然数幂方和由二项系数表示的系数a_i~(k)的公式,和由排列数表示的系数b_i~(k)的公式,证明了系数存在唯一性及系数间的若干重要性质,给出了计算系数的C-语言程序. 相似文献
66.
关于循环子半群的结构与数量问题及拟环的特征与结构 总被引:1,自引:0,他引:1
朱平 《纯粹数学与应用数学》2002,18(3):239-243,249
彻底解决了所有循环半群及其子群的结构和数量问题,并讨论了拟群分解问题,同时,对群论基本定理作了部分推广,并给出了定理的另一部分不可推广的反例,最后,建立了一类特殊环-拟环。 相似文献
67.
构造了由多模复共轭相干态|{Zj*}〉q、多模复共轭虚相干态|{iZj*}〉q和多模真空态|{Qj} 〉q这三态的线性叠加所组成的第Ⅲ类三态叠加多模叠加态光场|ψ3(3)〉q.利用多模压缩态理论研究了态|ψ3(3)〉q中广义磁场分量的任意偶数次广义非线性等幂次N次方Y压缩特性.结果发现:在压缩次数N取偶数,只要各模的初始相位φj(j=1,2,3,…,…,q),态间的初始相位差(θi-θ2)(i=1,3)和各单模相干态光场平均光子数Rj2之和 分别满足各自的取值条件,态|ψ3(3)〉q的广义磁场分量(即第一正交相位分量)就可呈现出周期性变化的、任意偶数次的广义非线性等幂次N次方Y压缩效应. 相似文献
68.
第Ⅷ类多模叠加态光场的偶阶N次方Y压缩 总被引:1,自引:1,他引:0
文章构造了第Ⅷ类两态叠加多模叠加态光场| Ψ(2)8>q,利用多模压缩态理论,详细研究了态|Ψ(2)8>q的广义非线性等幂次N次方Y压缩特性.结果发现态|Ψ(2)8>q是一种典型的非经典光场,它可呈出周期性变化的偶数阶等幂次N次方Y压缩效应;并且在一定的条件下, 本文的态|Ψ(2)8>q与文献3的态|Ψ(2)msc>q这两者之间可呈现出"等幂次N次方Y压缩简并"现象. 相似文献
69.
集对Fuzzy格及其在格表示论中的应用 总被引:1,自引:0,他引:1
用幂集格构造了集对 Fuzzy 格(这与用整数对构造有理数集有相似之处),并用它证明了完整的软代数表示定理,即定义了到自身的映射且有最大元和最小元的格为软代数的充要条件是它与某个集对 Fuzzy 格的子格同构.这样,与分配格在幂集 Boole 格中表示相对应,软代数在集对 Fuzzy 格中有表示,在理论上是很完美的 相似文献
70.